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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

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Pale refined oils are generally free from acidity or contain only traces (0-03%
as sulphuric acid). In dark oils, the acidity may reach 0-3% or, in exceptional
cases, 0-5%, but usually it does not exceed 0-15%. Mineral acids should not
be present.


The bituminous and pitchy residues from the distillation of mineral
oils (mazut, astatki or ostatki) are blackish, only slightly transparent, of
varying consistency, and of characteristic bituminous odour due to decom-
position products of difficultly volatile hydrocarbons.

The determinations and tests usually made are those of water, specific
gravity, distillation, flash and ignition points, viscosity, solid paraffin,
pitch and asphalt, the methods described for heavy oils being employed ;
the calorific power and the sulphur are determined as in crude petroleum.

As regards distillation, these residues often decompose at high tempera-
tures with formation of more volatile products, so that distillation by the
methods already indicated may yield an amount of distillate greater than
the true value. This inconvenience is obviated by distilling 100 grams
of the oil at reduced pressure (about 30 mm.)1 from a half-litre flask with
a side-tube connected with a sloping condenser, the lower end of which
passes through a cork in the neck of a distilling flask similar to that used
for the distillation of crude petroleum and having its side-tube in com-
munication with an ordinary water pump. The distillation is continued
until the thermometer marks 220°, the distillate being collected in the
second flask ; at the end of the operation, air is allowed into the apparatus
and the flask containing the distillate detached, the residue being then
distilled up to 300-310° at the ordinary pressure.

In determining the flash 'point, the residues often froth up at a tempera-
ture near 100° and overflow the vessel. In such cases the oil should be
dehydrated as indicated for heavy oils. Extinction of the flame at about
100° may be caused by residual traces of water in the product.

When the residues are to be used as fuel, the essential determinations are
those of the calorific power and sulphur ; the calorific value is about 10,000


Vaselines of two sorts are sold : the natural ones, which consist of hydro-
carbons semi-solid at the ordinary temperature, have colours varying from
white to yellowish-brown, exhibit slight fluorescence and are translucent,
somewhat sticky and ropy ; and the artificial ones, which consist of solutions
of solid hydrocarbons (paraffin wax or ceresine) in paraffin oil and are
usually white—sometimes, however, yellow or more or less brown—non-
fluorescent, opaque, not sticky and somewhat granular and readily separate
paraffin oil at a low temperature.

The examination of vaseline aims at ascertaining its quality and degree

1 Nasini and Villavecchia : Relazione sulle analisi e sidle ricerche eseguite nel Lab.
chim. Centrals delle Gabelle, Rome, 1890, pp. 104-106.the oils indicated above are subdivided into numerous types indicated